(1). Field of the Invention
This invention relates to an optical connector for use in multiple transmission circuits mounted in vehicles such as motorcars, a receptacle composing the optical connector, and a process for producing the receptacle.
(2). Description of the Related Art
As an optical connector, in which a sleeve lies between an optical fiber and an optical element module (sometimes called as light-receiving/light-emitting module, receiver/transmitter module, or fiber optic transceiver (FOT)), an optical connector proposed by the present applicant in Japanese Utility Model Publication No. H6-33443 has been generally known.
A pair of the above sleeves 101 and optical connector 102 are shown in FIG. 14.
Each sleeve 101, which is mounted in a receptacle 103 (an equipment-side connector) composing an optical connector 102, lies between a corresponding optical element module 104 (a light-emitting element module 104 or a light-receiving element module 104) also mounted in the receptacle 103 and an corresponding optical fiber 106 (only one of two fibers shown in FIG. 14, hereinafter the same) mounted in an optical plug 105 (an optical fiber-side connector) that is plugged into the receptacle 103 to assemble the optical connector 102. Thus, the sleeve 101 is regarded as a component of the optical connector, which is capable of making an optical connection between the optical element module 104 and the optical fiber 106.
The optical connector 102 consists of the receptacle 103 and the optical plug 105 that is plugged into the receptacle 103.
As shown in FIGS. 14 and 15, the receptacle 103 has a housing 107 made of synthetic resin, in which a pair of rooms 108 is provided to receive the corresponding optical element module 104 therein that is supported by a corresponding back sheet 109 consisting of resilient menber such as a rubber, the upper side of which is covered with a cap 110. Under a pair of the rooms 108, in each of which the corresponding optical element module 104 is received, a corresponding cylinder 112 is provided, which extends downward in such a manner that an axis of each cylinder 112 coincides with that of a corresponding lens 111. The sleeve 101 is inserted into the corresponding cylinder 112 to be installed therein.
The sleeve 101 is constructed in such a manner that an optical fiber 113 (multiple-mode plastic optical fiber) consisting of a core and clad (not shown in the figures) is glued to be fixed into a cylindrical holder 114 and both end surfaces of the sleeve 101 is superfinely polished.
On the other hand, as shown in FIGS. 14 and 16, the optical plug 105, which is plugged into the receptacle 103, contains: a pair of ferrule assemblies 115 each covering the corresponding optical fiber 106 in such a manner that an end surface of the optical fiber 106 is exposed; a plug housing 117 having a cylindrical partition 116 that receives and protects a pair of the ferrule assemblies 115 therein; a spring cap 118 that is fitted to the plug housing 117 to be fixed there; and a boot 119 that is fitted into the lower part of the spring cap 118.
In the plug housing 117, there is formed a pair of shoulders 117a, each of which is fitted to a corresponding flange 115a provided around the outer circumference of a lower portion of the corresponding ferrule assembly 115 and there is provided a pair of springs 120, each of which lies between the corresponding flange 115a and a corresponding inner cylinder 118a of the spring cap 118 so as to constantly press the ferrule assembly 115 upward.
As shown in FIG. 16, when the flange 115a is engaged with the shoulder 117a, an end a of the ferrule assembly 115, which corresponds to an end surface of the optical fiber 106, never come out from a front end b of the plug housing 117.
In the following, a connection between the receptacle 103 and the optical plug 105 is explained with reference to FIG. 14.
When the optical plug 105 is plugged into the receptacle 103, each cylinder 112 enters into the plug housing 117 and each ferrule assembly 115 simultaneously enters into the corresponding cylinder 112. The ferrule assembly 115 abuts against an end of the cylinder 112 and the spring 120 gives a moderate contact pressure therebetween.
In the above situation, the end a (see FIG. 16) and the sleeve 101 are arranged making minimun gap therebetween, thereby a loss caused by gap is controlled to be minimal.
In the above prior art, the sleeve 101 and the optical element module 104 are severally installed into the housing 107, causing a troublesome assembly process, inferior workability and high cost.
Further, the sleeve 101 and the optical element module 104 are separately constructed making a gap therebetween, causing a loss of light due to this gap as well as the above-mentioned loss of light due to the gap between the end a (see FIG. 16) and the sleeve 101. These losses of light might affect optical communication.
Furthermore, the receptacle 103 is produced through the steps of: forming the housing 107; producing the optical element module 104; producing the sleeve 101; forming the cap 110; and assembling in sequence thus produced components into the receptacle 103, causing too many steps and high cost thereby.
Further, the step of producing the optical element module 104 includes steps of producing a lead frame having the optical element and forming a molded portion, which protects the lead frame, using a transparent resin.
It is therefore an object of the present invention to solve the above problem and to provide a receptacle that is useful from the viewpoint of superior workability, low loss of light and low cost, and a process for producing the same. Another object of the present invention is to provide an inexpensive optical connector, which contributes for a better optical communication.
In order to accomplish the above object, a first aspect of the present invention is to provide a process for producing a receptacle, into which an optical plug having ferrule-mounted optical fibers at the end thereof is plugged, comprising the steps of: producing either one lead frame having an optical element, either a light-emitting element or a light-receiving element, or two lead frames consisting of one lead frame having a light-emitting element and another lead frame having a light-receiving element; forming a connector housing containing a socket cavity, into which the optical plug is plugged, a room for accommodating the lead frame and a cylinder being in communication therewith, wherein said cylinder is placed in such a manner that said cylinder is opposite to said end of the optical plug upon plugging of the optical plug into the socket cavity; forming a transparent, hollow and cylindrical clad on an inner circumferential surface of said cylinder after forming said connector housing; accommodating the lead frame into said room in such a manner that the optical element is placed on an axis of said cylinder in which the clad is formed; and producing an optical element module united with said connector housing by filling the inside of the clad and said room with a light-transmitting transparent resin having higher refractive index than that of the clad.
According to the first aspect of the present invention, the number of steps for producing a receptacle becomes small compared to that of a conventional process, enabling a reduction of cost as well as superior workability.
That is, by using the clad and the transparent resin filled therein, the optical element module itself functions as a conventional sleeve, saving a conventional process for making a sleeve. Accordingly, a superfine polishing for end surfaces of optical fibers, by fixing which into a cylindrical holder using glue, is not needed. Further, the optical element module is in one piece in a connector connector housing, resulting in that the optical element module needs no support, saving a conventinal process for making a cap. Furthermore, a conventional process for producing an optical element module as well as an assembly process can be simplified. Thus, superior workability for producing the recepacle is attained.
Since the optical element module itself has a function of a conventional sleeve, the optical element module functions in such a manner as if a conventional sleeve is opposite to an end of the optical fiber when the optical plug is plugged into the receptacle. Further, an optical loss caused by a gap, which is conventionally formed between a sleeve and optical element module, is minimized because of no such a gap, thereby enabling a better optical communication.
Preferably, the lead frame produced in said step of producing a lead frame is transferred to the following step with a carrier attached thereto, which is formed in a manufacture process thereof.
Accordingly, a form of the lead frame becomes stable in the following step, since the following step might be easily executed with a carrier attached the lead frame when the lead frame is composed of a plurality of members. Further, the lead frame is easily held since an area for holding the lead frame increases by a portion of the carrior, being particularly effective in such a case that the lead frame is held in-a mold. Furthermore, when two lead frames are received in the room, a positioning of the lead frames therebetween becomes easy. Therefore, further superior workability and low cost for producing the recepacle has been attained.
Preferably, the lead frame having the light-emitting element and the lead frame having the light-receiving element are alternately formed in the carrier in case of producing two lead frames.
Accordingly, the two lead frames can be received in the room of the connector housing at the same time. Therefore, further superior workability and low cost for producing the recepacle has been attained.
Preferably, a step of cutting the carrier is further included after said following step.
Accordingly, a cutting of the carrior is not necessarily needed in the step of producing the lead frame, enabling further superior workability and low cost for producing the recepacle.
Preferably, the clad is formed by double-shot molding.
Accordingly, a step of the assembly of the receptacle is further simplified, enabling further superior workability and low cost for producing the recepacle.
Preferably, the clad is produced in a separate step in advance and inserted in said step of forming the clad.
Accordingly, the number of steps is decreased even if the production and insertion of the clad is taken into consideration, enabling further superior workability and low cost for producing the recepacle.
Preferably, a light-shielding wall is formed in said room of the connector housing in case of producing two lead frames.
Accordingly, the light-receiving element never receives the light from the light-emitting element, preventing a cross talk and enabling a better optical communication.
A second aspect of the present invention is to provide a receptacle comprising: an optical element module containing either one lead frame having an optical element, either a light-emitting element or a light-receiving element, or two lead frames consisting of one lead frame having a light-emitting element and another lead frame having a light-receiving element; and a connector housing having a room for accommodating and placing the lead frame, into which an optical plug having ferrule-mounted optical fibers at the end thereof is plugged, wherein the connector housing contains a socket cavity for receiving the optical plug and a cylinder being in communication with the socket cavity and said room, the cylinder is formed and placed in such a manner that the cylinder is opposite to said end of the optical plug upon plugging of the optical plug into the socket cavity, the optical element module contains: a transparent, hollow and cylindrical clad formed on an inner circumferential surface of the cylinder; a core forming an optical waveguide in combination with the clad; and a molded portion united with the core for protecting the lead frame, and the core and the molded portion are made of a light-transmitting transparent resin, which is filled into the inside of the clad and said room, having higher refractive index than that of the clad.
According to the second aspect of the present invention, obtained is a receptacle, in which a connector housing and an optical element module are formed in one body by using a transparent resin that is filled into the inside of the clad and the room of the connector housing. An optical waveguide consisting of the clad and the transparent resin that is filled into the inside of the clad is formed, so that the optical element module itself has a function of a conventional sleeve. Further, obtained is a receptacle that has neither a conventional sleeve nor a cap. Accordingly, the producing and assembling processes are simplified, enabling superior workability and low cost for producing the recepacle. Furthermore, since the core and the molded portion are formed in one body, there is no such a gap between the sleeve and the optical element module that a conventional receptacle has, thereby minimizing an optical loss and enabling a better optical communication.
The optical element module functions in such a manner as if a conventional sleeve is opposite to an end of optical fibers when the optical plug is plugged into the receptacle. Accordingly, if an optical element in the lead frame is a light-emitting element, the light emitted from the light-emitting element is transmitted through the molded portion and the optical waveguide and then, entered into the end of the optical fibers. To the contrary, If an optical element in the lead frame is a light-receiving element, the light coming out from the optical fibers is transmitted through the optical waveguide and the molded portion and then, received by the light-receiving element. In case of the two lead frames that simultaneously has a light-emitting element and a light-receiving element, the optical element module has two functions descrived above.
A third aspect of the present invention is to provide an optical connector consisting of a receptacle produced by the process for producing a receptacle according to the first aspect of the present invention and an optical plug, which is plugged into the receptacle, having ferrule-mounted optical fibers at the end thereof.
According to the third aspect of the present invention, an inexpensive optical connector that contributes for a better optical communication is provided.
A fourth aspect of the present invention is to provide an optical connector consisting of the receptacle according to the second aspect of the present invention and an optical plug, which is plugged into the receptacle, having ferrule-mounted optical fibers at the end thereof.
According to the fourth aspect of the present invention, an inexpensive optical connector that contributes for a better optical communication is provided.